linux-kernel - Re: [RFC 03/16] KVM: selftests: handle encryption bits in page tables

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Message-ID: <31db4c63-218a-5b26-f6ed-d30113f95e29@redhat.com>
Date:   Thu, 21 Oct 2021 17:26:26 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Michael Roth <michael.roth@....com>,
        linux-kselftest@...r.kernel.org
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org,
        Nathan Tempelman <natet@...gle.com>,
        Marc Orr <marcorr@...gle.com>,
        Steve Rutherford <srutherford@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Mingwei Zhang <mizhang@...gle.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Varad Gautam <varad.gautam@...e.com>,
        Shuah Khan <shuah@...nel.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Ricardo Koller <ricarkol@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>
Subject: Re: [RFC 03/16] KVM: selftests: handle encryption bits in page tables

On 06/10/21 01:44, Michael Roth wrote:
> SEV guests rely on an encyption bit which resides within the range that
> current code treats as address bits. Guest code will expect these bits
> to be set appropriately in their page tables, whereas helpers like
> addr_gpa2hva() will expect these bits to be masked away prior to
> translation. Add proper handling for these cases.

This is not what you're doing below in addr_gpa2hva, though---or did I 
misunderstand?

I may be wrong due to not actually having written the code, but I'd 
prefer if most of these APIs worked only if the C bit has already been 
stripped.  In general it's quite unlikely for host code to deal with C=1 
pages, so it's worth pointing out explicitly the cases where it does.

Paolo

> @@ -1460,9 +1480,10 @@ void virt_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
>    * address providing the memory to the vm physical address is returned.
>    * A TEST_ASSERT failure occurs if no region containing gpa exists.
>    */
> -void *addr_gpa2hva(struct kvm_vm *vm, vm_paddr_t gpa)
> +void *addr_gpa2hva(struct kvm_vm *vm, vm_paddr_t gpa_raw)
>   {
>   	struct userspace_mem_region *region;