On Mon, May 05, 2025, Sasha Levin wrote: > From: Borislav Petkov <bp@xxxxxxxxx> > > [ Upstream commit 8442df2b49ed9bcd67833ad4f091d15ac91efd00 ] > > Add support for > > CPUID Fn8000_0021_EAX[31] (SRSO_MSR_FIX). If this bit is 1, it > indicates that software may use MSR BP_CFG[BpSpecReduce] to mitigate > SRSO. > > Enable BpSpecReduce to mitigate SRSO across guest/host boundaries. > > Switch back to enabling the bit when virtualization is enabled and to > clear the bit when virtualization is disabled because using a MSR slot > would clear the bit when the guest is exited and any training the guest > has done, would potentially influence the host kernel when execution > enters the kernel and hasn't VMRUN the guest yet. > > More detail on the public thread in Link below. > > Co-developed-by: Sean Christopherson <seanjc@xxxxxxxxxx> > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> > Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx> > Link: https://lore.kernel.org/r/20241202120416.6054-1-bp@xxxxxxxxxx > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > --- Can we please hold off on this until the fix lands[1]? This version introduces a very measurable performance regression[2] for non-KVM use cases. [1] https://lore.kernel.org/all/20250502223456.887618-1-seanjc@xxxxxxxxxx [2] https://www.phoronix.com/review/linux-615-amd-regression
