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Mon, 18 Aug 2025 03:15:11 -0700 (PDT) Message-ID: <5bf9b184-70fb-4698-a01e-e8cbcb05935f@suse.com> Date: Mon, 18 Aug 2025 12:15:10 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 1/4] xen/arm: Implement PSCI SYSTEM_SUSPEND call for guests To: Mykola Kvach Cc: Mykola Kvach , Stefano Stabellini , Julien Grall , Bertrand Marquis , Michal Orzel , Volodymyr Babchuk , Andrew Cooper , Anthony PERARD , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , xen-devel@lists.xenproject.org References: <205b2b354ff1d34d0e9ec4777ca3c94492f6d9d1.1755506449.git.mykola_kvach@epam.com> Content-Language: en-US From: Jan Beulich Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL In-Reply-To: <205b2b354ff1d34d0e9ec4777ca3c94492f6d9d1.1755506449.git.mykola_kvach@epam.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 18.08.2025 10:49, Mykola Kvach wrote: > --- a/xen/arch/arm/domain.c > +++ b/xen/arch/arm/domain.c > @@ -90,6 +90,16 @@ static void ctxt_switch_from(struct vcpu *p) > if ( is_idle_vcpu(p) ) > return; > > + /* Arch timer */ > + p->arch.cntkctl = READ_SYSREG(CNTKCTL_EL1); > + virt_timer_save(p); > + > + /* VGIC */ > + gic_save_state(p); > + > + if ( test_bit(_VPF_suspended, &p->pause_flags) ) > + return; As I had to look at the Arm side uses of the new bit to at least try to follow the comment further down, I came across this. And now I wonder: Why would one of the pause flags need special casing here? > @@ -1360,13 +1357,33 @@ void domain_resume(struct domain *d) > > for_each_vcpu ( d, v ) > { > + /* > + * No need to conditionally clear _VPF_suspended here: > + * - This bit is only set on Arm64, and only after a successful suspend. > + * - domain_resume_nopause() may also be called from paths other than > + * the suspend/resume flow, such as "soft-reset" actions (e.g., > + * on_poweroff), as part of the Xenstore control/shutdown protocol. > + * These require guest acknowledgement to complete the operation. > + * So clearing the bit unconditionally is safe. > + */ > + clear_bit(_VPF_suspended, &v->pause_flags); Seeing that you set this bit for a single vCPU in a domain only, I wonder why it needs to be a per-vCPU flag. Apart from this, with the comment I still fear I wouldn't feel capable of ack-ing this, as there's too much Arm-only interaction in here. It's not even clear whether this could easily be re-used by another port. Jan