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Merge branch 'kvm-e500-check-writable-pfn' into HEAD
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The new __kvm_faultin_pfn() function is upset by the fact that e500
KVM ignores host page permissions - __kvm_faultin requires a "writable"
outgoing argument, but e500 KVM is passing NULL.

While a simple fix would be possible that simply allows writable to
be NULL, it is quite ugly to have e500 KVM ignore completely the host
permissions and map readonly host pages as guest-writable.  Merge a more
complete fix and remove the VMA-based attempts at building huge shadow TLB
entries.  Using a PTE lookup, similar to what is done for x86, is better
and works with remap_pfn_range() because it does not assume that VM_PFNMAP
areas are contiguous.  Note that the same incorrect logic is there in
ARM's get_vma_page_shift() and RISC-V's kvm_riscv_gstage_ioremap().

Fortunately, for e500 most of the code is already there; it just has to
be changed to compute the range from find_linux_pte()'s output rather
than find_vma().  The new code works for both VM_PFNMAP and hugetlb
mappings, so the latter is removed.

Patches 2-5 were tested by the reporter, Christian Zigotzky.  Since
the difference with v1 is minimal, I am going to send it to Linus
today.
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Paolo Bonzini committed Jan 12, 2025
2 parents f07044d + 55f4db7 commit 71b7bf1
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Showing 2 changed files with 85 additions and 116 deletions.
2 changes: 2 additions & 0 deletions arch/powerpc/kvm/e500.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,8 @@ enum vcpu_ftr {
#define E500_TLB_BITMAP (1 << 30)
/* TLB1 entry is mapped by host TLB0 */
#define E500_TLB_TLB0 (1 << 29)
/* entry is writable on the host */
#define E500_TLB_WRITABLE (1 << 28)
/* bits [6-5] MAS2_X1 and MAS2_X0 and [4-0] bits for WIMGE */
#define E500_TLB_MAS2_ATTR (0x7f)

Expand Down
199 changes: 83 additions & 116 deletions arch/powerpc/kvm/e500_mmu_host.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -45,11 +45,14 @@ static inline unsigned int tlb1_max_shadow_size(void)
return host_tlb_params[1].entries - tlbcam_index - 1;
}

static inline u32 e500_shadow_mas3_attrib(u32 mas3, int usermode)
static inline u32 e500_shadow_mas3_attrib(u32 mas3, bool writable, int usermode)
{
/* Mask off reserved bits. */
mas3 &= MAS3_ATTRIB_MASK;

if (!writable)
mas3 &= ~(MAS3_UW|MAS3_SW);

#ifndef CONFIG_KVM_BOOKE_HV
if (!usermode) {
/* Guest is in supervisor mode,
Expand Down Expand Up @@ -242,17 +245,18 @@ static inline int tlbe_is_writable(struct kvm_book3e_206_tlb_entry *tlbe)
return tlbe->mas7_3 & (MAS3_SW|MAS3_UW);
}

static inline bool kvmppc_e500_ref_setup(struct tlbe_ref *ref,
static inline void kvmppc_e500_ref_setup(struct tlbe_ref *ref,
struct kvm_book3e_206_tlb_entry *gtlbe,
kvm_pfn_t pfn, unsigned int wimg)
kvm_pfn_t pfn, unsigned int wimg,
bool writable)
{
ref->pfn = pfn;
ref->flags = E500_TLB_VALID;
if (writable)
ref->flags |= E500_TLB_WRITABLE;

/* Use guest supplied MAS2_G and MAS2_E */
ref->flags |= (gtlbe->mas2 & MAS2_ATTRIB_MASK) | wimg;

return tlbe_is_writable(gtlbe);
}

static inline void kvmppc_e500_ref_release(struct tlbe_ref *ref)
Expand Down Expand Up @@ -305,14 +309,15 @@ static void kvmppc_e500_setup_stlbe(
{
kvm_pfn_t pfn = ref->pfn;
u32 pr = vcpu->arch.shared->msr & MSR_PR;
bool writable = !!(ref->flags & E500_TLB_WRITABLE);

BUG_ON(!(ref->flags & E500_TLB_VALID));

/* Force IPROT=0 for all guest mappings. */
stlbe->mas1 = MAS1_TSIZE(tsize) | get_tlb_sts(gtlbe) | MAS1_VALID;
stlbe->mas2 = (gvaddr & MAS2_EPN) | (ref->flags & E500_TLB_MAS2_ATTR);
stlbe->mas7_3 = ((u64)pfn << PAGE_SHIFT) |
e500_shadow_mas3_attrib(gtlbe->mas7_3, pr);
e500_shadow_mas3_attrib(gtlbe->mas7_3, writable, pr);
}

static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
Expand All @@ -321,15 +326,14 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
struct tlbe_ref *ref)
{
struct kvm_memory_slot *slot;
unsigned long pfn = 0; /* silence GCC warning */
unsigned int psize;
unsigned long pfn;
struct page *page = NULL;
unsigned long hva;
int pfnmap = 0;
int tsize = BOOK3E_PAGESZ_4K;
int ret = 0;
unsigned long mmu_seq;
struct kvm *kvm = vcpu_e500->vcpu.kvm;
unsigned long tsize_pages = 0;
pte_t *ptep;
unsigned int wimg = 0;
pgd_t *pgdir;
Expand All @@ -351,110 +355,12 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
slot = gfn_to_memslot(vcpu_e500->vcpu.kvm, gfn);
hva = gfn_to_hva_memslot(slot, gfn);

if (tlbsel == 1) {
struct vm_area_struct *vma;
mmap_read_lock(kvm->mm);

vma = find_vma(kvm->mm, hva);
if (vma && hva >= vma->vm_start &&
(vma->vm_flags & VM_PFNMAP)) {
/*
* This VMA is a physically contiguous region (e.g.
* /dev/mem) that bypasses normal Linux page
* management. Find the overlap between the
* vma and the memslot.
*/

unsigned long start, end;
unsigned long slot_start, slot_end;

pfnmap = 1;

start = vma->vm_pgoff;
end = start +
vma_pages(vma);

pfn = start + ((hva - vma->vm_start) >> PAGE_SHIFT);

slot_start = pfn - (gfn - slot->base_gfn);
slot_end = slot_start + slot->npages;

if (start < slot_start)
start = slot_start;
if (end > slot_end)
end = slot_end;

tsize = (gtlbe->mas1 & MAS1_TSIZE_MASK) >>
MAS1_TSIZE_SHIFT;

/*
* e500 doesn't implement the lowest tsize bit,
* or 1K pages.
*/
tsize = max(BOOK3E_PAGESZ_4K, tsize & ~1);

/*
* Now find the largest tsize (up to what the guest
* requested) that will cover gfn, stay within the
* range, and for which gfn and pfn are mutually
* aligned.
*/

for (; tsize > BOOK3E_PAGESZ_4K; tsize -= 2) {
unsigned long gfn_start, gfn_end;
tsize_pages = 1UL << (tsize - 2);

gfn_start = gfn & ~(tsize_pages - 1);
gfn_end = gfn_start + tsize_pages;

if (gfn_start + pfn - gfn < start)
continue;
if (gfn_end + pfn - gfn > end)
continue;
if ((gfn & (tsize_pages - 1)) !=
(pfn & (tsize_pages - 1)))
continue;

gvaddr &= ~((tsize_pages << PAGE_SHIFT) - 1);
pfn &= ~(tsize_pages - 1);
break;
}
} else if (vma && hva >= vma->vm_start &&
is_vm_hugetlb_page(vma)) {
unsigned long psize = vma_kernel_pagesize(vma);

tsize = (gtlbe->mas1 & MAS1_TSIZE_MASK) >>
MAS1_TSIZE_SHIFT;

/*
* Take the largest page size that satisfies both host
* and guest mapping
*/
tsize = min(__ilog2(psize) - 10, tsize);

/*
* e500 doesn't implement the lowest tsize bit,
* or 1K pages.
*/
tsize = max(BOOK3E_PAGESZ_4K, tsize & ~1);
}

mmap_read_unlock(kvm->mm);
}

if (likely(!pfnmap)) {
tsize_pages = 1UL << (tsize + 10 - PAGE_SHIFT);
pfn = __kvm_faultin_pfn(slot, gfn, FOLL_WRITE, NULL, &page);
if (is_error_noslot_pfn(pfn)) {
if (printk_ratelimit())
pr_err("%s: real page not found for gfn %lx\n",
__func__, (long)gfn);
return -EINVAL;
}

/* Align guest and physical address to page map boundaries */
pfn &= ~(tsize_pages - 1);
gvaddr &= ~((tsize_pages << PAGE_SHIFT) - 1);
pfn = __kvm_faultin_pfn(slot, gfn, FOLL_WRITE, &writable, &page);
if (is_error_noslot_pfn(pfn)) {
if (printk_ratelimit())
pr_err("%s: real page not found for gfn %lx\n",
__func__, (long)gfn);
return -EINVAL;
}

spin_lock(&kvm->mmu_lock);
Expand All @@ -472,14 +378,13 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
* can't run hence pfn won't change.
*/
local_irq_save(flags);
ptep = find_linux_pte(pgdir, hva, NULL, NULL);
ptep = find_linux_pte(pgdir, hva, NULL, &psize);
if (ptep) {
pte_t pte = READ_ONCE(*ptep);

if (pte_present(pte)) {
wimg = (pte_val(pte) >> PTE_WIMGE_SHIFT) &
MAS2_WIMGE_MASK;
local_irq_restore(flags);
} else {
local_irq_restore(flags);
pr_err_ratelimited("%s: pte not present: gfn %lx,pfn %lx\n",
Expand All @@ -488,10 +393,72 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
goto out;
}
}
writable = kvmppc_e500_ref_setup(ref, gtlbe, pfn, wimg);
local_irq_restore(flags);

if (psize && tlbsel == 1) {
unsigned long psize_pages, tsize_pages;
unsigned long start, end;
unsigned long slot_start, slot_end;

psize_pages = 1UL << (psize - PAGE_SHIFT);
start = pfn & ~(psize_pages - 1);
end = start + psize_pages;

slot_start = pfn - (gfn - slot->base_gfn);
slot_end = slot_start + slot->npages;

if (start < slot_start)
start = slot_start;
if (end > slot_end)
end = slot_end;

tsize = (gtlbe->mas1 & MAS1_TSIZE_MASK) >>
MAS1_TSIZE_SHIFT;

/*
* Any page size that doesn't satisfy the host mapping
* will fail the start and end tests.
*/
tsize = min(psize - PAGE_SHIFT + BOOK3E_PAGESZ_4K, tsize);

/*
* e500 doesn't implement the lowest tsize bit,
* or 1K pages.
*/
tsize = max(BOOK3E_PAGESZ_4K, tsize & ~1);

/*
* Now find the largest tsize (up to what the guest
* requested) that will cover gfn, stay within the
* range, and for which gfn and pfn are mutually
* aligned.
*/

for (; tsize > BOOK3E_PAGESZ_4K; tsize -= 2) {
unsigned long gfn_start, gfn_end;
tsize_pages = 1UL << (tsize - 2);

gfn_start = gfn & ~(tsize_pages - 1);
gfn_end = gfn_start + tsize_pages;

if (gfn_start + pfn - gfn < start)
continue;
if (gfn_end + pfn - gfn > end)
continue;
if ((gfn & (tsize_pages - 1)) !=
(pfn & (tsize_pages - 1)))
continue;

gvaddr &= ~((tsize_pages << PAGE_SHIFT) - 1);
pfn &= ~(tsize_pages - 1);
break;
}
}

kvmppc_e500_ref_setup(ref, gtlbe, pfn, wimg, writable);
kvmppc_e500_setup_stlbe(&vcpu_e500->vcpu, gtlbe, tsize,
ref, gvaddr, stlbe);
writable = tlbe_is_writable(stlbe);

/* Clear i-cache for new pages */
kvmppc_mmu_flush_icache(pfn);
Expand Down

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