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x86/sev: Prepare for using the RMPREAD instruction to access the RMP
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The RMPREAD instruction returns an architecture defined format of an RMP
entry. This is the preferred method for examining RMP entries.

In preparation for using the RMPREAD instruction, convert the existing code
that directly accesses the RMP to map the raw RMP information into the
architecture defined format.

RMPREAD output returns a status bit for the 2MB region status. If the input
page address is 2MB aligned and any other pages within the 2MB region are
assigned, then 2MB region status will be set to 1. Otherwise, the 2MB region
status will be set to 0.

For systems that do not support RMPREAD, calculating this value would require
looping over all of the RMP table entries within that range until one is found
with the assigned bit set. Since this bit is not defined in the current
format, and so not used today, do not incur the overhead associated with
calculating it.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nikunj A Dadhania <nikunj@amd.com>
Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Link: https://lore.kernel.org/r/da49d5af1eb7f9039f35f14a32ca091efb2dd818.1733172653.git.thomas.lendacky@amd.com
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Tom Lendacky authored and Borislav Petkov (AMD) committed Dec 13, 2024
1 parent fac04ef commit 3e43c60
Showing 1 changed file with 94 additions and 38 deletions.
132 changes: 94 additions & 38 deletions arch/x86/virt/svm/sev.c
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Original file line number Diff line number Diff line change
Expand Up @@ -31,10 +31,29 @@
#include <asm/iommu.h>

/*
* The RMP entry format is not architectural. The format is defined in PPR
* Family 19h Model 01h, Rev B1 processor.
* The RMP entry information as returned by the RMPREAD instruction.
*/
struct rmpentry {
u64 gpa;
u8 assigned :1,
rsvd1 :7;
u8 pagesize :1,
hpage_region_status :1,
rsvd2 :6;
u8 immutable :1,
rsvd3 :7;
u8 rsvd4;
u32 asid;
} __packed;

/*
* The raw RMP entry format is not architectural. The format is defined in PPR
* Family 19h Model 01h, Rev B1 processor. This format represents the actual
* entry in the RMP table memory. The bitfield definitions are used for machines
* without the RMPREAD instruction (Zen3 and Zen4), otherwise the "hi" and "lo"
* fields are only used for dumping the raw data.
*/
struct rmpentry_raw {
union {
struct {
u64 assigned : 1,
Expand Down Expand Up @@ -62,7 +81,7 @@ struct rmpentry {
#define PFN_PMD_MASK GENMASK_ULL(63, PMD_SHIFT - PAGE_SHIFT)

static u64 probed_rmp_base, probed_rmp_size;
static struct rmpentry *rmptable __ro_after_init;
static struct rmpentry_raw *rmptable __ro_after_init;
static u64 rmptable_max_pfn __ro_after_init;

static LIST_HEAD(snp_leaked_pages_list);
Expand Down Expand Up @@ -249,8 +268,8 @@ static int __init snp_rmptable_init(void)
rmptable_start += RMPTABLE_CPU_BOOKKEEPING_SZ;
rmptable_size = probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ;

rmptable = (struct rmpentry *)rmptable_start;
rmptable_max_pfn = rmptable_size / sizeof(struct rmpentry) - 1;
rmptable = (struct rmpentry_raw *)rmptable_start;
rmptable_max_pfn = rmptable_size / sizeof(struct rmpentry_raw) - 1;

cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/rmptable_init:online", __snp_enable, NULL);

Expand All @@ -272,48 +291,77 @@ static int __init snp_rmptable_init(void)
*/
device_initcall(snp_rmptable_init);

static struct rmpentry *get_rmpentry(u64 pfn)
static struct rmpentry_raw *get_raw_rmpentry(u64 pfn)
{
if (WARN_ON_ONCE(pfn > rmptable_max_pfn))
if (!rmptable)
return ERR_PTR(-ENODEV);

if (unlikely(pfn > rmptable_max_pfn))
return ERR_PTR(-EFAULT);

return &rmptable[pfn];
return rmptable + pfn;
}

static int get_rmpentry(u64 pfn, struct rmpentry *e)
{
struct rmpentry_raw *e_raw;

e_raw = get_raw_rmpentry(pfn);
if (IS_ERR(e_raw))
return PTR_ERR(e_raw);

/*
* Map the raw RMP table entry onto the RMPREAD output format.
* The 2MB region status indicator (hpage_region_status field) is not
* calculated, since the overhead could be significant and the field
* is not used.
*/
memset(e, 0, sizeof(*e));
e->gpa = e_raw->gpa << PAGE_SHIFT;
e->asid = e_raw->asid;
e->assigned = e_raw->assigned;
e->pagesize = e_raw->pagesize;
e->immutable = e_raw->immutable;

return 0;
}

static struct rmpentry *__snp_lookup_rmpentry(u64 pfn, int *level)
static int __snp_lookup_rmpentry(u64 pfn, struct rmpentry *e, int *level)
{
struct rmpentry *large_entry, *entry;
struct rmpentry e_large;
int ret;

if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
return ERR_PTR(-ENODEV);
return -ENODEV;

entry = get_rmpentry(pfn);
if (IS_ERR(entry))
return entry;
ret = get_rmpentry(pfn, e);
if (ret)
return ret;

/*
* Find the authoritative RMP entry for a PFN. This can be either a 4K
* RMP entry or a special large RMP entry that is authoritative for a
* whole 2M area.
*/
large_entry = get_rmpentry(pfn & PFN_PMD_MASK);
if (IS_ERR(large_entry))
return large_entry;
ret = get_rmpentry(pfn & PFN_PMD_MASK, &e_large);
if (ret)
return ret;

*level = RMP_TO_PG_LEVEL(large_entry->pagesize);
*level = RMP_TO_PG_LEVEL(e_large.pagesize);

return entry;
return 0;
}

int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level)
{
struct rmpentry *e;
struct rmpentry e;
int ret;

e = __snp_lookup_rmpentry(pfn, level);
if (IS_ERR(e))
return PTR_ERR(e);
ret = __snp_lookup_rmpentry(pfn, &e, level);
if (ret)
return ret;

*assigned = !!e->assigned;
*assigned = !!e.assigned;
return 0;
}
EXPORT_SYMBOL_GPL(snp_lookup_rmpentry);
Expand All @@ -326,20 +374,28 @@ EXPORT_SYMBOL_GPL(snp_lookup_rmpentry);
*/
static void dump_rmpentry(u64 pfn)
{
struct rmpentry_raw *e_raw;
u64 pfn_i, pfn_end;
struct rmpentry *e;
int level;
struct rmpentry e;
int level, ret;

e = __snp_lookup_rmpentry(pfn, &level);
if (IS_ERR(e)) {
pr_err("Failed to read RMP entry for PFN 0x%llx, error %ld\n",
pfn, PTR_ERR(e));
ret = __snp_lookup_rmpentry(pfn, &e, &level);
if (ret) {
pr_err("Failed to read RMP entry for PFN 0x%llx, error %d\n",
pfn, ret);
return;
}

if (e->assigned) {
if (e.assigned) {
e_raw = get_raw_rmpentry(pfn);
if (IS_ERR(e_raw)) {
pr_err("Failed to read RMP contents for PFN 0x%llx, error %ld\n",
pfn, PTR_ERR(e_raw));
return;
}

pr_info("PFN 0x%llx, RMP entry: [0x%016llx - 0x%016llx]\n",
pfn, e->lo, e->hi);
pfn, e_raw->lo, e_raw->hi);
return;
}

Expand All @@ -358,16 +414,16 @@ static void dump_rmpentry(u64 pfn)
pfn, pfn_i, pfn_end);

while (pfn_i < pfn_end) {
e = __snp_lookup_rmpentry(pfn_i, &level);
if (IS_ERR(e)) {
pr_err("Error %ld reading RMP entry for PFN 0x%llx\n",
PTR_ERR(e), pfn_i);
e_raw = get_raw_rmpentry(pfn_i);
if (IS_ERR(e_raw)) {
pr_err("Error %ld reading RMP contents for PFN 0x%llx\n",
PTR_ERR(e_raw), pfn_i);
pfn_i++;
continue;
}

if (e->lo || e->hi)
pr_info("PFN: 0x%llx, [0x%016llx - 0x%016llx]\n", pfn_i, e->lo, e->hi);
if (e_raw->lo || e_raw->hi)
pr_info("PFN: 0x%llx, [0x%016llx - 0x%016llx]\n", pfn_i, e_raw->lo, e_raw->hi);
pfn_i++;
}
}
Expand Down

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