From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-45.mta0.migadu.com (out-45.mta0.migadu.com [91.218.175.45]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C66CD79DE for ; Fri, 31 Mar 2023 16:11:02 +0000 (UTC) Date: Fri, 31 Mar 2023 16:10:55 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1680279060; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=g+lxPASBKZp7epsEpoEJ/xRVGiXQ6rwMrwRM8RJUtv8=; b=HT161TKGYpXwxa27Wt/Me8h3bRTsaxZZVQ1lM81yLNldqxj+ohAfxekTF4Q5crAdOg9Miz wuT57QyL/h3QUmFxbYr1xwPMilGg8kljwZ72VzY0RhyEU6iofYj2lWLwk44gtZFbI+Otm5 jhPMhl+IaR01o7zC056fIGZu79AVWeM= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Fuad Tabba Cc: kvmarm@lists.linux.dev, maz@kernel.org, oupton@google.com, will@kernel.org, pbonzini@redhat.com, james.morse@arm.com, alexandru.elisei@arm.com, suzuki.poulose@arm.com, reijiw@google.com, ricarkol@google.com, rananta@google.com, jingzhangos@google.com Subject: Re: [PATCH v3] KVM: arm64: Advertise ID_AA64PFR0_EL1.CSV2/3 to protected VMs Message-ID: References: <20230331131218.2063233-1-tabba@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230331131218.2063233-1-tabba@google.com> X-Migadu-Flow: FLOW_OUT Hi Fuad, Thanks for catching the masking issue in v2. Few comments: On Fri, Mar 31, 2023 at 02:12:18PM +0100, Fuad Tabba wrote: > The existing pKVM code attempts to do that using a value nit: it is more readable if you restate what 'that' is in the changelog, even if it is already in the shortlog. > initialized to 0, but never set. To advertise csv2/3 to protected > guests, pass the csv values to hyp when initializing hyp's view > of guests' ID_AA64PFR0_EL1. > > Similar to non-protected KVM, these are system-wide, rather than > per cpu, for simplicity. > > Fixes: 6c30bfb18d0b ("KVM: arm64: Add handlers for protected VM System Registers") > Signed-off-by: Fuad Tabba > > Changes from V2: Fix masking not to affect bits other than CSV2/3. Commentary like this that you don't want to appear in the commit when applied should appear below the '---' > --- I.e. right here. > arch/arm64/kvm/arm.c | 24 ++++++++++++++++++- > .../arm64/kvm/hyp/include/nvhe/fixed_config.h | 5 +++- > arch/arm64/kvm/hyp/nvhe/sys_regs.c | 7 ------ > 3 files changed, 27 insertions(+), 9 deletions(-) > > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index 3bd732eaf087..0ae927c99fa1 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -1889,9 +1889,31 @@ static int __init do_pkvm_init(u32 hyp_va_bits) > return ret; > } > > +static u64 get_hyp_id_aa64pfr0_el1(void) > +{ > + u64 mask = ~0ULL; > + > + /* > + * Track whether the system isn't affected by spectre/meltown in the > + * hypervisor's view of id_aa64pfr0_el1, used for protected VMs. > + * Although this is per-CPU, we make it global for simplicity, e.g., not > + * to have to worry about vcpu migration. > + * > + * Unlike for non-protected VMs, userspace cannot override this for > + * protected VMs. > + */ > + if (arm64_get_spectre_v2_state() != SPECTRE_UNAFFECTED) > + mask &= ~ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV2); > + > + if (arm64_get_meltdown_state() != SPECTRE_UNAFFECTED) > + mask &= ~ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_CSV3); Doesn't this introduce a subtle change to the way that the CSV[23] values are constrained in KVM? At least for 'normal' VMs we constrain both fields to having a max value of 1. -- Thanks, Oliver