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

Tom Lendacky
2021-08-17T15:26:29Z

On 8/17/21 5:02 AM, Borislav Petkov wrote:
> 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().

I was trying to keep the sev_active() changes separate... so even though
it's an SME thing, I kept it here. But I can move it to the previous
patch, it just might look strange.

>
>> 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.

Yup, I'll change them all.

>
>> @@ -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.

Ok.

Thanks,
Tom

>
> Thx.
>