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[34.90.134.61]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-aa68f4eb962sm281095666b.3.2024.12.10.07.15.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Dec 2024 07:15:57 -0800 (PST) Date: Tue, 10 Dec 2024 15:15:54 +0000 From: Quentin Perret To: Fuad Tabba Cc: Marc Zyngier , Oliver Upton , Joey Gouly , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Vincent Donnefort , Sebastian Ene , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 01/18] KVM: arm64: Change the layout of enum pkvm_page_state Message-ID: References: <20241203103735.2267589-1-qperret@google.com> <20241203103735.2267589-2-qperret@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Hey Fuad, On Tuesday 10 Dec 2024 at 12:59:44 (+0000), Fuad Tabba wrote: > Hi Quentin, > > On Tue, 3 Dec 2024 at 10:37, Quentin Perret wrote: > > > > The 'concrete' (a.k.a non-meta) page states are currently encoded using > > software bits in PTEs. For performance reasons, the abstract > > pkvm_page_state enum uses the same bits to encode these states as that > > makes conversions from and to PTEs easy. > > > > In order to prepare the ground for moving the 'concrete' state storage > > to the hyp vmemmap, re-arrange the enum to use bits 0 and 1 for this > > purpose. > > > > No functional changes intended. > > > > Signed-off-by: Quentin Perret > > --- > > arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 17 ++++++++++------- > > 1 file changed, 10 insertions(+), 7 deletions(-) > > > > diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h > > index 0972faccc2af..ca3177481b78 100644 > > --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h > > +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h > > @@ -24,25 +24,28 @@ > > */ > > enum pkvm_page_state { > > PKVM_PAGE_OWNED = 0ULL, > > - PKVM_PAGE_SHARED_OWNED = KVM_PGTABLE_PROT_SW0, > > - PKVM_PAGE_SHARED_BORROWED = KVM_PGTABLE_PROT_SW1, > > - __PKVM_PAGE_RESERVED = KVM_PGTABLE_PROT_SW0 | > > - KVM_PGTABLE_PROT_SW1, > > + PKVM_PAGE_SHARED_OWNED = BIT(0), > > + PKVM_PAGE_SHARED_BORROWED = BIT(1), > > + __PKVM_PAGE_RESERVED = BIT(0) | BIT(1), > > > > /* Meta-states which aren't encoded directly in the PTE's SW bits */ > > - PKVM_NOPAGE, > > + PKVM_NOPAGE = BIT(2), > > }; > > +#define PKVM_PAGE_META_STATES_MASK (~(BIT(0) | BIT(1))) > > > > #define PKVM_PAGE_STATE_PROT_MASK (KVM_PGTABLE_PROT_SW0 | KVM_PGTABLE_PROT_SW1) > > static inline enum kvm_pgtable_prot pkvm_mkstate(enum kvm_pgtable_prot prot, > > enum pkvm_page_state state) > > { > > - return (prot & ~PKVM_PAGE_STATE_PROT_MASK) | state; > > + BUG_ON(state & PKVM_PAGE_META_STATES_MASK); > > This is a slight change in functionality, having a BUG_ON instead of > just masking out illegal states. Is it necessary? Yep, this is arguably a bit zealous. Passing e.g. PKVM_NOPAGE to pkvm_mkstate() would be properly bogus, so having a WARN_ON() or BUG_ON() in there is still a good thing, but it should be done in a separate patch. I'll rework in v3. > > + prot &= ~PKVM_PAGE_STATE_PROT_MASK; > > + prot |= FIELD_PREP(PKVM_PAGE_STATE_PROT_MASK, state); > > + return prot; > > } > > > > static inline enum pkvm_page_state pkvm_getstate(enum kvm_pgtable_prot prot) > > { > > - return prot & PKVM_PAGE_STATE_PROT_MASK; > > + return FIELD_GET(PKVM_PAGE_STATE_PROT_MASK, prot); > > } > > > > struct host_mmu { > > -- > > 2.47.0.338.g60cca15819-goog > >