Messages in this thread | | | Date | Tue, 26 Apr 2022 08:19:53 +0200 | Subject | Re: [PATCH v2 0/2] Dirtying, failing memop: don't indicate suppression | From | Christian Borntraeger <> |
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Am 25.04.22 um 19:29 schrieb Janis Schoetterl-Glausch: > On 4/25/22 18:30, Christian Borntraeger wrote: >> Am 25.04.22 um 12:01 schrieb Janis Schoetterl-Glausch: >>> If a memop fails due to key checked protection, after already having >>> written to the guest, don't indicate suppression to the guest, as that >>> would imply that memory wasn't modified. >>> >>> This could be considered a fix to the code introducing storage key >>> support, however this is a bug in KVM only if we emulate an >>> instructions writing to an operand spanning multiple pages, which I >>> don't believe we do. >>> >> >> Thanks applied. I think it makes sense for 5.18 nevertheless. > > Janosch had some concerns because the protection code being 000 implies > that the effective address in the TEID is unpredictable. > Let's see if he chimes in.
z/VM does exactly the same on key protection crossing a page boundary. The architecture was written in a way to allow all zeros exactly for this case. (hypervisor emulation of key protection crossing pages). This is even true for ESOP-2. See Figure 3-5 or figure 3-8 (the first line) which allows to NOT have a valid address in the TEID for key controlled protection.
The only question is, do we need to change the suppression parameter in access_guest_with_key
(mode != GACC_STORE) || (idx == 0)
to also check for prot != PROT_TYPE_KEYC ? I think we do not need this as we have checked other reasons before.
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