When running identity mapped and depending on the kernel configuration, it is possible that cc_platform_has() can have compiler generated code that uses jump tables. This causes a boot failure because the jump table uses un-mapped kernel virtual addresses, not identity mapped addresses. This has been seen with CONFIG_RETPOLINE=n. Similar to sme_encrypt_kernel(), use an open-coded direct check for the status of SNP rather than trying to eliminate the jump table. This preserves any code optimization in cc_platform_has() that can be useful post boot. It also limits the changes to SEV-specific files so that future compiler features won't necessarily require possible build changes just because they are not compatible with running identity mapped. Link: https://bugzilla.kernel.org/show_bug.cgi?id=216385 Link: https://lore.kernel.org/all/YqfabnTRxFSM+LoX@xxxxxxxxxx/ Cc: <stable@xxxxxxxxxxxxxxx> # 5.19.x Reported-by: Sean Christopherson <seanjc@xxxxxxxxxx> Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx> --- arch/x86/kernel/sev.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c index 63dc626627a0..4f84c3f11af5 100644 --- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -701,7 +701,13 @@ static void __init early_set_pages_state(unsigned long paddr, unsigned int npage void __init early_snp_set_memory_private(unsigned long vaddr, unsigned long paddr, unsigned int npages) { - if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) + /* + * This can be invoked in early boot while running identity mapped, so + * use an open coded check for SNP instead of using cc_platform_has(). + * This eliminates worries about jump tables or checking boot_cpu_data + * in the cc_platform_has() function. + */ + if (!(sev_status & MSR_AMD64_SEV_SNP_ENABLED)) return; /* @@ -717,7 +723,13 @@ void __init early_snp_set_memory_private(unsigned long vaddr, unsigned long padd void __init early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr, unsigned int npages) { - if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) + /* + * This can be invoked in early boot while running identity mapped, so + * use an open coded check for SNP instead of using cc_platform_has(). + * This eliminates worries about jump tables or checking boot_cpu_data + * in the cc_platform_has() function. + */ + if (!(sev_status & MSR_AMD64_SEV_SNP_ENABLED)) return; /* Invalidate the memory pages before they are marked shared in the RMP table. */ -- 2.37.2
