From ac517965a5a12d685f1e7a7f77e64503167f87d5 Mon Sep 17 00:00:00 2001 From: Tom Lendacky Date: Mon, 2 Dec 2024 14:50:50 -0600 Subject: [PATCH] x86/sev: Map only the RMP table entries instead of the full RMP range In preparation for support of a segmented RMP table, map only the RMP table entries. The RMP bookkeeping area is only ever accessed when first enabling SNP and does not need to remain mapped. To accomplish this, split the initialization of the RMP bookkeeping area and the initialization of the RMP entry area. The RMP bookkeeping area will be mapped only while it is being initialized. Signed-off-by: Tom Lendacky Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Nikunj A Dadhania Reviewed-by: Neeraj Upadhyay Reviewed-by: Ashish Kalra Link: https://lore.kernel.org/r/22f179998d319834f49c13a8c01187fbf0fd308d.1733172653.git.thomas.lendacky@amd.com --- arch/x86/virt/svm/sev.c | 36 +++++++++++++++++++++++++++++++----- 1 file changed, 31 insertions(+), 5 deletions(-) diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c index 0df378951ac79..2899c2e28db9d 100644 --- a/arch/x86/virt/svm/sev.c +++ b/arch/x86/virt/svm/sev.c @@ -173,6 +173,23 @@ void __init snp_fixup_e820_tables(void) __snp_fixup_e820_tables(probed_rmp_base + probed_rmp_size); } +static bool __init clear_rmptable_bookkeeping(void) +{ + void *bk; + + bk = memremap(probed_rmp_base, RMPTABLE_CPU_BOOKKEEPING_SZ, MEMREMAP_WB); + if (!bk) { + pr_err("Failed to map RMP bookkeeping area\n"); + return false; + } + + memset(bk, 0, RMPTABLE_CPU_BOOKKEEPING_SZ); + + memunmap(bk); + + return true; +} + /* * Do the necessary preparations which are verified by the firmware as * described in the SNP_INIT_EX firmware command description in the SNP @@ -210,12 +227,17 @@ static int __init snp_rmptable_init(void) goto nosnp; } - rmptable_start = memremap(probed_rmp_base, probed_rmp_size, MEMREMAP_WB); + /* Map only the RMP entries */ + rmptable_start = memremap(probed_rmp_base + RMPTABLE_CPU_BOOKKEEPING_SZ, + probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ, + MEMREMAP_WB); if (!rmptable_start) { pr_err("Failed to map RMP table\n"); goto nosnp; } + rmptable_size = probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ; + /* * Check if SEV-SNP is already enabled, this can happen in case of * kexec boot. @@ -224,7 +246,14 @@ static int __init snp_rmptable_init(void) if (val & MSR_AMD64_SYSCFG_SNP_EN) goto skip_enable; - memset(rmptable_start, 0, probed_rmp_size); + /* Zero out the RMP bookkeeping area */ + if (!clear_rmptable_bookkeeping()) { + memunmap(rmptable_start); + goto nosnp; + } + + /* Zero out the RMP entries */ + memset(rmptable_start, 0, rmptable_size); /* Flush the caches to ensure that data is written before SNP is enabled. */ wbinvd_on_all_cpus(); @@ -235,9 +264,6 @@ static int __init snp_rmptable_init(void) on_each_cpu(snp_enable, NULL, 1); skip_enable: - rmptable_start += RMPTABLE_CPU_BOOKKEEPING_SZ; - rmptable_size = probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ; - rmptable = (struct rmpentry_raw *)rmptable_start; rmptable_max_pfn = rmptable_size / sizeof(struct rmpentry_raw) - 1;