On 15.10.24 14:31, Kirill A. Shutemov wrote:
On Tue, Oct 15, 2024 at 12:12:51PM +0200, Jürgen Groß wrote:On 15.10.24 11:58, Kirill A. Shutemov wrote:AMD SEV-SNP and Intel TDX have limited access to MTRR: either it is not advertised in CPUID or it cannot be programmed (on TDX, due to #VE on CR0.CD clear). This results in guests using uncached mappings where it shouldn't and pmd/pud_set_huge() failures due to non-uniform memory type reported by mtrr_type_lookup(). Override MTRR state, making it WB by default as the kernel does for Hyper-V guests. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Suggested-by: Binbin Wu <binbin.wu@xxxxxxxxx> Cc: Juergen Gross <jgross@xxxxxxxx> Cc: Tom Lendacky <thomas.lendacky@xxxxxxx> --- arch/x86/kernel/kvm.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 263f8aed4e2c..21e9e4845354 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -37,6 +37,7 @@ #include <asm/apic.h> #include <asm/apicdef.h> #include <asm/hypervisor.h> +#include <asm/mtrr.h> #include <asm/tlb.h> #include <asm/cpuidle_haltpoll.h> #include <asm/ptrace.h> @@ -980,6 +981,9 @@ static void __init kvm_init_platform(void) } kvmclock_init(); x86_platform.apic_post_init = kvm_apic_init; + + /* Set WB as the default cache mode for SEV-SNP and TDX */ + mtrr_overwrite_state(NULL, 0, MTRR_TYPE_WRBACK);Do you really want to do this for _all_ KVM guests? I'd expect this call to be conditional on TDX or SEV-SNP.mtrr_overwrite_state() checks it internally.
Ah, right, I forgot I added that check on request by Boris. :-) Reviewed-by: Juergen Gross <jgross@xxxxxxxx> Juergen
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