Re: [PATCH v2 06/12] x86/sev: Replace occurrences of sev_active() with prot_guest_has()

Borislav Petkov
2021-08-17T10:02:14Z

On Fri, Aug 13, 2021 at 11:59:25AM -0500, Tom Lendacky wrote:
> diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
> index 8e7b517ad738..66ff788b79c9 100644
> --- a/arch/x86/kernel/machine_kexec_64.c
> +++ b/arch/x86/kernel/machine_kexec_64.c
> @@ -167,7 +167,7 @@ static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
> }
> pte = pte_offset_kernel(pmd, vaddr);
>
> - if (sev_active())
> + if (prot_guest_has(PATTR_GUEST_MEM_ENCRYPT))
> prot = PAGE_KERNEL_EXEC;
>
> set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, prot));
> @@ -207,7 +207,7 @@ static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
> level4p = (pgd_t *)__va(start_pgtable);
> clear_page(level4p);
>
> - if (sev_active()) {
> + if (prot_guest_has(PATTR_GUEST_MEM_ENCRYPT)) {
> info.page_flag |= _PAGE_ENC;
> info.kernpg_flag |= _PAGE_ENC;
> }
> @@ -570,12 +570,12 @@ void arch_kexec_unprotect_crashkres(void)
> */
> int arch_kexec_post_alloc_pages(void *vaddr, unsigned int pages, gfp_t gfp)
> {
> - if (sev_active())
> + if (!prot_guest_has(PATTR_HOST_MEM_ENCRYPT))
> return 0;
>
> /*
> - * If SME is active we need to be sure that kexec pages are
> - * not encrypted because when we boot to the new kernel the
> + * If host memory encryption is active we need to be sure that kexec
> + * pages are not encrypted because when we boot to the new kernel the
> * pages won't be accessed encrypted (initially).
> */

That hunk belongs logically into the previous patch which removes
sme_active().

> return set_memory_decrypted((unsigned long)vaddr, pages);
> @@ -583,12 +583,12 @@ int arch_kexec_post_alloc_pages(void *vaddr, unsigned int pages, gfp_t gfp)
>
> void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages)
> {
> - if (sev_active())
> + if (!prot_guest_has(PATTR_HOST_MEM_ENCRYPT))
> return;
>
> /*
> - * If SME is active we need to reset the pages back to being
> - * an encrypted mapping before freeing them.
> + * If host memory encryption is active we need to reset the pages back
> + * to being an encrypted mapping before freeing them.
> */
> set_memory_encrypted((unsigned long)vaddr, pages);
> }
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index e8ccab50ebf6..b69f5ac622d5 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -25,6 +25,7 @@
> #include <linux/pagemap.h>
> #include <linux/swap.h>
> #include <linux/rwsem.h>
> +#include <linux/protected_guest.h>
>
> #include <asm/apic.h>
> #include <asm/perf_event.h>
> @@ -457,7 +458,7 @@ static int has_svm(void)
> return 0;
> }
>
> - if (sev_active()) {
> + if (prot_guest_has(PATTR_SEV)) {
> pr_info("KVM is unsupported when running as an SEV guest\n");
> return 0;

Same question as for PATTR_SME. PATTR_GUEST_MEM_ENCRYPT should be enough.

> @@ -373,7 +373,7 @@ int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size)
> * up under SME the trampoline area cannot be encrypted, whereas under SEV
> * the trampoline area must be encrypted.
> */
> -bool sev_active(void)
> +static bool sev_active(void)
> {
> return sev_status & MSR_AMD64_SEV_ENABLED;
> }
> @@ -382,7 +382,6 @@ static bool sme_active(void)
> {
> return sme_me_mask && !sev_active();
> }
> -EXPORT_SYMBOL_GPL(sev_active);

Just get rid of it altogether.

Thx.

--
Regards/Gruss,
Boris.