On 23/05/2025 20:02, Atish Patra wrote:
On 5/23/25 9:27 AM, Radim KrÄmáŠwrote:
2025-05-23T17:29:49+02:00, Clément Léger cleger@rivosinc.com:
On 23/05/2025 15:05, Radim Krčmář wrote:
2025-05-23T12:19:30+02:00, Clément Léger cleger@rivosinc.com:
+++ b/arch/riscv/kvm/vcpu_sbi_fwft.c +static const enum sbi_fwft_feature_t kvm_fwft_defined_features[] = { + SBI_FWFT_MISALIGNED_EXC_DELEG, + SBI_FWFT_LANDING_PAD, + SBI_FWFT_SHADOW_STACK, + SBI_FWFT_DOUBLE_TRAP, + SBI_FWFT_PTE_AD_HW_UPDATING, + SBI_FWFT_POINTER_MASKING_PMLEN, +};
How will userspace control which subset of these features is allowed in the guest?
(We can reuse the KVM SBI extension interface if we don't want to add a FWFT specific ONE_REG.)
Hi Radim,
I didn't looked at that part. But most likely using the kvm one reg interface seems ok like what is done for STA ? We could have per feature override with one reg per feature.
Sounds fine.
Yeah. We can have a follow up series for SBI FWFT state that allows user space to toggle each state individually.
Is this something blocking though ? We'd like to merge FWFT once SBI 3.0 is ratified so that would be nice not delaying it too much. I'll take a look at it to see if it isn't too long to implement.
Not blocking, but I would at least default FWFT to disabled, because current userspace cannot handle [14/14]. (Well... save/restore was probably broken even before, but let's try to not make it worse. :])
User space can not enable or disable misaligned access delegation as there is no interface for now rightly pointed by you. I guess supporting that would be quicker than fixing the broader guest save/restore anyways. Isn't it ?
We can have the patches ready for the next MW for FWFT one reg interface.
Yeah sure I'll work on that in the meantime.
Thanks.
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