From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A05C1258CF5; Wed, 12 Mar 2025 19:45:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741808706; cv=none; b=D+QObN6Ii+OlqB6qSr8ajSH4IoyijZbjmBKsb0Zu7YMqjnqKiBnwGNz4XIDVAVvKo6ep3h6b6lsv/MeUwDHXXgj8j2U1+e50RRnSz1rBPvc/0Isy7R8O1BqmYVjsfxjqvOgUqMTdaOvAnwmYcHOS/Ci+OdtZJoODQAvAZlyCK3U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741808706; c=relaxed/simple; bh=hNYjTn6zdVR9mjDQJg9s/8yzeDoJWMMYD7pocvfTf7U=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=c+xjceRXjtw3tRzHmh/p7N/zNbC2VH7gYvZpcTV/ffskeIRSFUrmTEE7dBGjnbccIYwtys62WWg7KQJ4JZGjGGtfO032aXDflFqncB5J6/mhXoWbsIh8vqeovNtJn9QB6exfd++D7Glx5Kuw9nQCS/gSLrM81LCyrEqgcS6zNZo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=KY6veRW/; arc=none smtp.client-ip=13.77.154.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="KY6veRW/" Received: from [10.0.0.114] (c-67-182-156-199.hsd1.wa.comcast.net [67.182.156.199]) by linux.microsoft.com (Postfix) with ESMTPSA id 54861210B155; Wed, 12 Mar 2025 12:45:03 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 54861210B155 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1741808704; bh=VPZyhneTbQ5N9T3+s+eAs9kmLhZ3O/aRW/7FQa9FcNM=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=KY6veRW/TYvXYRqlrieko87RB02NPbqemVQu9wxZBtiO6QjiU/jl4VJVIXKn+Qbmp KpAwxXbEdKbtO9dv8eLqZC9Td03MtvGs74WCxdYf1T7Bp+epAKWMipnCA5JUxKkrav rtBkKkfD6I461kYIQ4heEXnpybyaQIEDWL4XSiiY= Message-ID: <5e3e8c30-912c-4fe3-bfac-1ae21242473b@linux.microsoft.com> Date: Wed, 12 Mar 2025 12:44:38 -0700 Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 07/10] Drivers: hv: Introduce per-cpu event ring tail To: Tianyu Lan Cc: linux-hyperv@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-acpi@vger.kernel.org, kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, mhklinux@outlook.com, decui@microsoft.com, catalin.marinas@arm.com, will@kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, daniel.lezcano@linaro.org, joro@8bytes.org, robin.murphy@arm.com, arnd@arndb.de, jinankjain@linux.microsoft.com, muminulrussell@gmail.com, skinsburskii@linux.microsoft.com, mrathor@linux.microsoft.com, ssengar@linux.microsoft.com, apais@linux.microsoft.com, Tianyu.Lan@microsoft.com, stanislav.kinsburskiy@gmail.com, gregkh@linuxfoundation.org, vkuznets@redhat.com, prapal@linux.microsoft.com, muislam@microsoft.com, anrayabh@linux.microsoft.com, rafael@kernel.org, lenb@kernel.org, corbet@lwn.net References: <1740611284-27506-1-git-send-email-nunodasneves@linux.microsoft.com> <1740611284-27506-8-git-send-email-nunodasneves@linux.microsoft.com> Content-Language: en-US From: Nuno Das Neves In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 3/10/2025 6:01 AM, Tianyu Lan wrote: > On Thu, Feb 27, 2025 at 7:09 AM Nuno Das Neves > wrote: >> >> Add a pointer hv_synic_eventring_tail to track the tail pointer for the >> SynIC event ring buffer for each SINT. >> >> This will be used by the mshv driver, but must be tracked independently >> since the driver module could be removed and re-inserted. >> >> Signed-off-by: Nuno Das Neves >> Reviewed-by: Wei Liu > > It's better to expose a function to check the tail instead of exposing > hv_synic_eventring_tail directly. > What is the advantage of using a function for this? We need to both set and get the tail. > BTW, how does mshv driver use hv_synic_eventring_tail? Which patch > uses it in this series? > This variable stores indices into the synic eventring page (one for each SINT, and per-cpu). Each SINT has a ringbuffer of u32 messages. The tail index points to the latest one. This is only used for doorbell messages today. The message in this case is a port number which is used to lookup and invoke a callback, which signals ioeventfd(s), to notify the VMM of a guest MMIO write. It is used in patch 10. Thanks Nuno > Thanks. > > >> --- >> drivers/hv/hv_common.c | 34 ++++++++++++++++++++++++++++++++-- >> 1 file changed, 32 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c >> index 252fd66ad4db..2763cb6d3678 100644 >> --- a/drivers/hv/hv_common.c >> +++ b/drivers/hv/hv_common.c >> @@ -68,6 +68,16 @@ static void hv_kmsg_dump_unregister(void); >> >> static struct ctl_table_header *hv_ctl_table_hdr; >> >> +/* >> + * Per-cpu array holding the tail pointer for the SynIC event ring buffer >> + * for each SINT. >> + * >> + * We cannot maintain this in mshv driver because the tail pointer should >> + * persist even if the mshv driver is unloaded. >> + */ >> +u8 __percpu **hv_synic_eventring_tail; >> +EXPORT_SYMBOL_GPL(hv_synic_eventring_tail); >> + >> /* >> * Hyper-V specific initialization and shutdown code that is >> * common across all architectures. Called from architecture >> @@ -90,6 +100,9 @@ void __init hv_common_free(void) >> >> free_percpu(hyperv_pcpu_input_arg); >> hyperv_pcpu_input_arg = NULL; >> + >> + free_percpu(hv_synic_eventring_tail); >> + hv_synic_eventring_tail = NULL; >> } >> >> /* >> @@ -372,6 +385,11 @@ int __init hv_common_init(void) >> BUG_ON(!hyperv_pcpu_output_arg); >> } >> >> + if (hv_root_partition()) { >> + hv_synic_eventring_tail = alloc_percpu(u8 *); >> + BUG_ON(hv_synic_eventring_tail == NULL); >> + } >> + >> hv_vp_index = kmalloc_array(nr_cpu_ids, sizeof(*hv_vp_index), >> GFP_KERNEL); >> if (!hv_vp_index) { >> @@ -460,6 +478,7 @@ void __init ms_hyperv_late_init(void) >> int hv_common_cpu_init(unsigned int cpu) >> { >> void **inputarg, **outputarg; >> + u8 **synic_eventring_tail; >> u64 msr_vp_index; >> gfp_t flags; >> const int pgcount = hv_output_page_exists() ? 2 : 1; >> @@ -472,8 +491,8 @@ int hv_common_cpu_init(unsigned int cpu) >> inputarg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg); >> >> /* >> - * hyperv_pcpu_input_arg and hyperv_pcpu_output_arg memory is already >> - * allocated if this CPU was previously online and then taken offline >> + * The per-cpu memory is already allocated if this CPU was previously >> + * online and then taken offline >> */ >> if (!*inputarg) { >> mem = kmalloc(pgcount * HV_HYP_PAGE_SIZE, flags); >> @@ -485,6 +504,17 @@ int hv_common_cpu_init(unsigned int cpu) >> *outputarg = (char *)mem + HV_HYP_PAGE_SIZE; >> } >> >> + if (hv_root_partition()) { >> + synic_eventring_tail = (u8 **)this_cpu_ptr(hv_synic_eventring_tail); >> + *synic_eventring_tail = kcalloc(HV_SYNIC_SINT_COUNT, >> + sizeof(u8), flags); >> + >> + if (unlikely(!*synic_eventring_tail)) { >> + kfree(mem); >> + return -ENOMEM; >> + } >> + } >> + >> if (!ms_hyperv.paravisor_present && >> (hv_isolation_type_snp() || hv_isolation_type_tdx())) { >> ret = set_memory_decrypted((unsigned long)mem, pgcount); >> -- >> 2.34.1 >> >> > >