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charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-OriginatorOrg: epam.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: GV1PR03MB10456.eurprd03.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 8dd6900c-157a-43a8-3ccb-08ddd5281029 X-MS-Exchange-CrossTenant-originalarrivaltime: 06 Aug 2025 20:30:20.2914 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b41b72d0-4e9f-4c26-8a69-f949f367c91d X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: pHjC9thHKoMwWWpaFY36bz8QECUktdd1Aaw6L590iqlGZ0aivOWb7h/stAjRqSZjFB/xCefuvhYjC8xc6rEoihfk3nD94TbEsDsi5O7T/jE= X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM9PR03MB7107 Hi Oliver, Oliver Upton writes: > On Wed, Aug 06, 2025 at 02:17:55PM +0000, Volodymyr Babchuk wrote: >> Previously this code update only vCPU's in-memory value, which is good, >> but not enough, as there will be no context switch after exiting >> exception handler, so in-memory value will not get into actual >> register. >>=20 >> It worked good enough for VHE guests because KVM code tried fast path, >> which of course updated real PAR_EL1. >>=20 >> Signed-off-by: Volodymyr Babchuk >> --- >> arch/arm64/kvm/sys_regs.c | 6 ++++++ >> 1 file changed, 6 insertions(+) >>=20 >> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c >> index 7b8a0a6f26468..ab2b5e261d312 100644 >> --- a/arch/arm64/kvm/sys_regs.c >> +++ b/arch/arm64/kvm/sys_regs.c >> @@ -3463,6 +3463,9 @@ static bool handle_at_s1e2(struct kvm_vcpu *vcpu, = struct sys_reg_params *p, >> =20 >> __kvm_at_s1e2(vcpu, op, p->regval); >> =20 >> + /* No context switch happened, so we need to update PAR_EL1 manually *= / >> + write_sysreg(vcpu_read_sys_reg(vcpu, PAR_EL1), par_el1); >> + > > Ok, this had me thoroughly confused for a moment. The bug is actually in > kvm_write_sys_reg() which is supposed to update the sysreg value when > things are loaded on the CPU. __kvm_at_s1e2() is doing the right thing > by calling this accessor. > > For registers like PAR_EL1 that don't have an EL2->EL1 mapping we assume > they belong to the EL1 context and thus are in-memory when in a hyp > context. TPIDR(RO)_EL0 is similarly affected. > > This is a bit of an ugly hack, but something like the following should > get things working if you're able to test it: Yep, it is working pretty good. Will you send the patch? I'll add my Tested-by. Or will you prefer that I'll send the patch with your Suggested-by: ? [...] --=20 WBR, Volodymyr=