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Thu, 01 Apr 2021 02:45:27 -0700 (PDT) Received: from localhost ([1.128.222.144]) by smtp.gmail.com with ESMTPSA id s22sm4958637pjs.42.2021.04.01.02.45.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Apr 2021 02:45:27 -0700 (PDT) Date: Thu, 01 Apr 2021 19:45:21 +1000 From: Nicholas Piggin Subject: Re: [PATCH v4 04/46] KVM: PPC: Book3S HV: Prevent radix guests from setting LPCR[TC] To: Paul Mackerras References: <20210323010305.1045293-1-npiggin@gmail.com> <20210323010305.1045293-5-npiggin@gmail.com> In-Reply-To: MIME-Version: 1.0 Message-Id: <1617269806.5qka0ltce0.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Excerpts from Paul Mackerras's message of March 31, 2021 2:34 pm: > On Tue, Mar 23, 2021 at 11:02:23AM +1000, Nicholas Piggin wrote: >> This bit only applies to hash partitions. >>=20 >> Signed-off-by: Nicholas Piggin >> --- >> arch/powerpc/kvm/book3s_hv.c | 6 ++++++ >> arch/powerpc/kvm/book3s_hv_nested.c | 3 +-- >> 2 files changed, 7 insertions(+), 2 deletions(-) >>=20 >> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c >> index c5de7e3f22b6..1ffb0902e779 100644 >> --- a/arch/powerpc/kvm/book3s_hv.c >> +++ b/arch/powerpc/kvm/book3s_hv.c >> @@ -1645,6 +1645,12 @@ static int kvm_arch_vcpu_ioctl_set_sregs_hv(struc= t kvm_vcpu *vcpu, >> */ >> unsigned long kvmppc_filter_lpcr_hv(struct kvmppc_vcore *vc, unsigned l= ong lpcr) >> { >> + struct kvm *kvm =3D vc->kvm; >> + >> + /* LPCR_TC only applies to HPT guests */ >> + if (kvm_is_radix(kvm)) >> + lpcr &=3D ~LPCR_TC; >=20 > I'm not sure I see any benefit from this, and it is a little extra > complexity. Principle of allowing a guest to mess with as little HV state as=20 possible (but not littler), which I think is a good one to follow. >=20 >> /* On POWER8 and above, userspace can modify AIL */ >> if (!cpu_has_feature(CPU_FTR_ARCH_207S)) >> lpcr &=3D ~LPCR_AIL; >> diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book= 3s_hv_nested.c >> index f7b441b3eb17..851e3f527eb2 100644 >> --- a/arch/powerpc/kvm/book3s_hv_nested.c >> +++ b/arch/powerpc/kvm/book3s_hv_nested.c >> @@ -140,8 +140,7 @@ static void sanitise_hv_regs(struct kvm_vcpu *vcpu, = struct hv_guest_state *hr) >> /* >> * Don't let L1 change LPCR bits for the L2 except these: >> */ >> - mask =3D LPCR_DPFD | LPCR_ILE | LPCR_TC | LPCR_AIL | LPCR_LD | >> - LPCR_LPES | LPCR_MER; >> + mask =3D LPCR_DPFD | LPCR_ILE | LPCR_AIL | LPCR_LD | LPCR_LPES | LPCR_= MER; >=20 > Doesn't this make it completely impossible to set TC for any guest? Argh, yes Fabiano pointed this out in an earlier rev and I didn't fix this hunk after adding the filter bit. Thanks. Thanks, Nick