Re: [PATCH 4/4] powerpc/powernv: Remove POWER9 PVR version check for entry and uaccess flushes
From: Joel Stanley <joel@jms.id.au>
Date: 2021-05-04 00:52:21
On Mon, 3 May 2021 at 13:04, Nicholas Piggin [off-list ref] wrote:
These aren't necessarily POWER9 only, and it's not to say some new vulnerability may not get discovered on other processors for which we would like the flexibility of having the workaround enabled by firmware. Remove the restriction that they only apply to POWER9.
I was wondering how these worked which led me to reviewing your patch. From what I could see, these are enabled by default (SEC_FTR_DEFAULT in arch/powerpc/include/asm/security_features.h), so unless all non-POWER9 machines have set the "please don't" bit in their firmware this patch will enable the feature for those machines. Is that what you wanted?
quoted hunk ↗ jump to hunk
Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/platforms/powernv/setup.c | 9 --------- 1 file changed, 9 deletions(-)diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c index a8db3f153063..6ec67223f8c7 100644 --- a/arch/powerpc/platforms/powernv/setup.c +++ b/arch/powerpc/platforms/powernv/setup.c@@ -122,15 +122,6 @@ static void pnv_setup_security_mitigations(void) type = L1D_FLUSH_ORI; } - /* - * If we are non-Power9 bare metal, we don't need to flush on kernel - * entry or after user access: they fix a P9 specific vulnerability. - */ - if (!pvr_version_is(PVR_POWER9)) { - security_ftr_clear(SEC_FTR_L1D_FLUSH_ENTRY); - security_ftr_clear(SEC_FTR_L1D_FLUSH_UACCESS); - } - enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) && \ (security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR) || \ security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV)); --2.23.0