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Fri, 04 Sep 2026 01:33:36 -0700 (PDT) Message-ID: <879f5184-351e-4f12-947b-d66eef5fee77@suse.com> Date: Fri, 4 Sep 2026 10:33:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 12/39] xen/riscv: implement vCPU context switching To: Baptiste Le Duc Cc: xen-devel@lists.xenproject.org, Romain Caritey , Zheng Zhang , Alistair Francis , Connor Davis , Andrew Cooper , Anthony PERARD , Michal Orzel , Julien Grall , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Stefano Stabellini , Oleksii Kurochko References: <8848874c69f00fbfcf6ad75a39e28479a4cdd08b.1787838835.git.oleksii.kurochko@gmail.com> <1788510380.8631fc262581453bbf619ec5b2062170.1a06b86a349000c4f3@vates.tech> 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: <1788510380.8631fc262581453bbf619ec5b2062170.1a06b86a349000c4f3@vates.tech> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-purgate-ID: tlsNG-d62444/1788510817-BE07B757-C627DF4F/0/0 X-purgate-type: clean X-purgate-size: 2872 On 04.09.2026 10:26, Baptiste Le Duc wrote: >> @@ -329,6 +333,169 @@ int arch_domain_create(struct domain *d, >> return rc; >> } >> >> +static void save_csr_regs(struct vcpu *vcpu) >> +{ >> + /* >> + * There is no need to save these CSRs as only hypervisor writes them in >> + * restore_csr_regs() and guest can't access them so they shouldn't be >> + * stored here. Keep them commented here just for symmetry with the >> + * restore CSRs register part. >> + * >> + * vcpu->arch.hedeleg = csr_read(CSR_HEDELEG); >> + * vcpu->arch.hideleg = csr_read(CSR_HIDELEG); >> + * vcpu->arch.henvcfg = csr_read64(CSR_HENVCFG); >> + * vcpu->arch.hcounteren = csr_read(CSR_HCOUNTEREN); >> + * vcpu->arch.htimedelta = csr_read64(CSR_HTIMEDELTA); >> + * >> + * if ( riscv_isa_extension_available(NULL, RISCV_ISA_EXT_smstateen) ) >> + * vcpu->arch.hstateen0 = csr_read(CSR_HSTATEEN0); >> + */ >> + >> + vcpu->arch.hvip = csr_read(CSR_HVIP); >> + >> + vcpu->arch.vsstatus = csr_read(CSR_VSSTATUS); >> + vcpu->arch.vsie = csr_read(CSR_VSIE); > > >> + vcpu->arch.vstvec = csr_read(CSR_VSTVEC); >> + vcpu->arch.vsscratch = csr_read(CSR_VSSCRATCH); >> + vcpu->arch.vscause = csr_read(CSR_VSCAUSE); >> + vcpu->arch.vstval = csr_read(CSR_VSTVAL); >> + vcpu->arch.vsepc = csr_read(CSR_VSEPC); >> +} >> + >> +static void restore_csr_regs(struct vcpu *vcpu) >> +{ >> + csr_write(CSR_HEDELEG, vcpu->arch.hedeleg); >> + csr_write(CSR_HIDELEG, vcpu->arch.hideleg); >> + csr_write(CSR_HVIP, vcpu->arch.hvip); >> + csr_write64(CSR_HENVCFG, vcpu->arch.henvcfg); >> + csr_write(CSR_HCOUNTEREN, vcpu->arch.hcounteren); >> + csr_write64(CSR_HTIMEDELTA, vcpu->arch.htimedelta); >> + >> + if ( riscv_isa_extension_available(NULL, RISCV_ISA_EXT_smstateen) ) >> + csr_write(CSR_HSTATEEN0, vcpu->arch.hstateen0); >> + >> + csr_write(CSR_VSSTATUS, vcpu->arch.vsstatus); >> + csr_write(CSR_VSIE, vcpu->arch.vsie); > > >> + csr_write(CSR_VSTVEC, vcpu->arch.vstvec); >> + csr_write(CSR_VSSCRATCH, vcpu->arch.vsscratch); >> + csr_write(CSR_VSCAUSE, vcpu->arch.vscause); >> + csr_write(CSR_VSTVAL, vcpu->arch.vstval); >> + csr_write(CSR_VSEPC, vcpu->arch.vsepc); >> +} >> + >> +static void ctxt_switch_from(struct vcpu *p) > Is it expected to have diverse names for the vcpu arg? Above it's vcpu, > here it's p (I assume it's for `previous` but I think the _from alone is > enough to understand) and below it's n. Shouldn't be better to keep the same name? Context switch code is special, and using p and n can be warranted there. Everywhere else it should be v, nothing else (and I said so to Oleksii more than once before). Unless, of course, multiple vCPU-s come into play at the same time. Jan