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Wed, 04 Feb 2026 02:39:09 -0800 (PST) Message-ID: Date: Wed, 4 Feb 2026 11:39:07 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 13/16] xen/riscv: implement reprogram_timer() via SBI To: Oleksii Kurochko Cc: Alistair Francis , Connor Davis , Andrew Cooper , Anthony PERARD , Michal Orzel , Julien Grall , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Stefano Stabellini , Romain Caritey , xen-devel@lists.xenproject.org References: <732635f43fb80daec332f78d4442b56bf5dfda98.1769099885.git.oleksii.kurochko@gmail.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: <732635f43fb80daec332f78d4442b56bf5dfda98.1769099885.git.oleksii.kurochko@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 22.01.2026 17:47, Oleksii Kurochko wrote: > @@ -40,6 +43,46 @@ static void __init preinit_dt_xen_time(void) > cpu_khz = rate / 1000; > } > > +int reprogram_timer(s_time_t timeout) > +{ > + uint64_t deadline, now; > + int rc; > + > + if ( timeout == 0 ) > + { > + /* Disable timers */ > + csr_clear(CSR_SIE, BIT(IRQ_S_TIMER, UL)); For here and below: Is it guaranteed that the SIE bit is writable? The privileged spec looks to have provisions for the case that it isn't (together with the corresponding SIP bit). As to the comment - why plural here, when ... > + return 1; > + } > + > + deadline = ns_to_ticks(timeout) + boot_clock_cycles; > + now = get_cycles(); > + if ( deadline <= now ) > + return 0; > + > + /* Enable timer */ > + csr_set(CSR_SIE, BIT(IRQ_S_TIMER, UL)); ... it's singular here? Also in both cases, isn't it the timer interrupt you enable, not the timer itself? > + /* > + * TODO: When the SSTC extension is supported, it would be preferable to > + * use the supervisor timer registers directly here for better > + * performance, since an SBI call and context switch would no longer > + * be required. I think you mean a mode switch here, not a context one? Jan > + * This would also reduce reliance on a specific SBI implementation. > + * For example, it is not ideal to panic() if sbi_set_timer() returns > + * a non-zero value. Currently it can return 0 or -ENOSUPP, and > + * without SSTC we still need an implementation because only the > + * M-mode timer is available, and it can only be programmed in > + * M-mode. > + */ > + if ( (rc = sbi_set_timer(deadline)) ) > + panic("%s: timer wasn't set because: %d\n", __func__, rc); > + > + return 1; > +} > + > void __init preinit_xen_time(void) > { > if ( acpi_disabled )