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[109.243.64.38]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-608b4adea28sm7349891a12.69.2025.06.17.00.09.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 17 Jun 2025 00:09:20 -0700 (PDT) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: fe03ae6b-4b49-11f0-b894-0df219b8e170 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1750144161; x=1750748961; darn=lists.xenproject.org; h=in-reply-to:from:content-language:references:cc:to:subject :user-agent:mime-version:date:message-id:from:to:cc:subject:date :message-id:reply-to; bh=bEeP4aV8ba20MLCuov8VPQ/W6UufLD63nz1kwE8kDM8=; b=UrdYiyNN8x6PJfw6pWtVTEAanH14tEC+oYRJv31aOZY5plXikbY1BakTKx6z00xlYg JaTc1PGHT6zhLNrOeHx7jx5pYhs5CWGPK4cCKjjPtGpj2KgtcgnFv8YXrnRrREU2rR5s tRanvR2myXDd/BWmBiYeL4HBWkNeb7Ymr9mdKen2K20cBlyBfJG/8xnZggITlNPzvuj1 BGZFkDkyEz7JshaGgSXCZM9lnMHJalweAPczZP6qg2JUdKb4JkA0zVf2UptbwC4MZPAK 7mNZWYk3TnQyP74FSzKho3I7XN4IikShU98lg9Y4k8sR0ddZoiWPYY0rPn6vIDoZsVQQ RyDg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1750144161; x=1750748961; h=in-reply-to:from:content-language:references:cc:to:subject :user-agent:mime-version:date:message-id:x-gm-message-state:from:to :cc:subject:date:message-id:reply-to; bh=bEeP4aV8ba20MLCuov8VPQ/W6UufLD63nz1kwE8kDM8=; b=P9uXj+uM0hQgUqn2wYffNYrO90Hdzn5ZNOHW9ECCGzpslmup1y/1mg4ffhnblxUh1u oDKxBEdzD++KmRtjJMdq2QQTGyVs4jxq7fieBUbPXFu4w/HLEDk7L8mGuCP+fL2Zfy1c 6H/6DmBHKp1xww0Onm1KuYO1MDQvqj2FErqP41lMYYjihEWU2p+VktfvVNrrqMFvPg65 smEY/HIb2Oddc5oDGTk5Sn903RBVj2sdqdY7zQCD0AAuIjKZtH0YddDsy78dqzLYkkT9 6I+DxPIwHLspHhZb1Sqm1/37c+8YW6CAr8cCP6H1r4KkcwKSNpQf4kzXiXwwBFssOpZd ADHg== X-Forwarded-Encrypted: i=1; AJvYcCVTcdDOdRb04RNI7bpI8bsQLhZ1yRLyKScxKbbhQ8jr3YU0wojLxWwtYinAB+KgTosox2qJ/uSjA+c=@lists.xenproject.org X-Gm-Message-State: AOJu0YySFJPHAPhZzVL6ykeXhw0E+HA9G/yVyp7/CCxOD8zantS/iYzr 7jP5NVdrL9N6OR4OhgeKFHaYUcMdiJrPmT5ebcXw6y8bDxsPOjwWuJtG X-Gm-Gg: ASbGncvHCCFtg175ClSdmoKiCdeLpx76wSXqvmhSj8L/opC9PKPGXopwlcj6MNfKuCA DVOBVLNpGeIBysdKC1DVk7y7GOJPT546aV7iHbAPsawWspvFbjdU6RhsuDw6D0kARyVAre7HsGO T40j6x1H05iCQstwJ1d0/6l4lqCxn7rEM6aVsjnQktECpKQY3n0cMKIASitWNUQOINpX+9owJSO 2wOmBCPmA1K6VVTKJI54lRmskWzHp+bjwVlKODFBwI9mX/9eh4blEuJc9Cw5Y+AYtdSKJBNbbpU nUuNaqedozNkGkhiRuJQom8+orFzFVKv3BIaHZMI3uk6JeWzo2icIfxQIiwY4MLt/BtzXcbpzAh T/28BaTMntj9wVARFp2OdAtRLf1Yod6g9SBPq1cF1agceHg== X-Google-Smtp-Source: AGHT+IFf9Lk4JFAOLQ9bBRkot0eXijwQ7ZtO0Uo9kGqH6jEbcELVSX8PwjSuaL3Ew85HiYtbHDtRvA== X-Received: by 2002:a05:6402:26c7:b0:608:47ee:dc4 with SMTP id 4fb4d7f45d1cf-608d09cf155mr9933526a12.23.1750144160711; Tue, 17 Jun 2025 00:09:20 -0700 (PDT) Content-Type: multipart/alternative; boundary="------------B0Qy7QKMeOBJiRuzXBIFI7sN" Message-ID: <313996d5-8801-4aed-92f8-e96d57dd9429@gmail.com> Date: Tue, 17 Jun 2025 09:09:19 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 8/8] pdx: introduce a command line option for offset compression To: Roger Pau Monne , xen-devel@lists.xenproject.org Cc: Community Manager , Andrew Cooper , Anthony PERARD , Michal Orzel , Jan Beulich , Julien Grall , Stefano Stabellini References: <20250611171636.5674-1-roger.pau@citrix.com> <20250611171636.5674-9-roger.pau@citrix.com> Content-Language: en-US From: Oleksii Kurochko In-Reply-To: <20250611171636.5674-9-roger.pau@citrix.com> This is a multi-part message in MIME format. --------------B0Qy7QKMeOBJiRuzXBIFI7sN Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 6/11/25 7:16 PM, Roger Pau Monne wrote: > Allow controlling whether to attempt PDX compression, and which algorithm > to use to calculate the coefficients. Document the option and also add a > CHANGELOG entry for the newly added feature. > > Note the work has been originally done to cope with the new Intel > Sapphire/Granite Rapids, however the compression is not explicitly tied to > Intel or x86, and hence could be helpful on other architectures. > > Signed-off-by: Roger Pau Monné > --- > CHANGELOG.md | 3 +++ > docs/misc/xen-command-line.pandoc | 22 ++++++++++++++++++ > xen/common/pdx.c | 38 +++++++++++++++++++++++++++---- > 3 files changed, 59 insertions(+), 4 deletions(-) LGTM: Reviewed-by: Oleksii Kurochko Thanks. ~ Oleksii > > diff --git a/CHANGELOG.md b/CHANGELOG.md > index 23215a8cc1e6..48327f03078f 100644 > --- a/CHANGELOG.md > +++ b/CHANGELOG.md > @@ -20,6 +20,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/) > table or foreign memory. > > ### Added > + - Introduce new PDX compression algorithm to cope with Intel Sapphire and > + Granite Rapids having sparse memory maps. > + > - On x86: > - Option to attempt to fixup p2m page-faults on PVH dom0. > - Resizable BARs is supported for PVH dom0. > diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc > index b0eadd2c5d58..06819576a06b 100644 > --- a/docs/misc/xen-command-line.pandoc > +++ b/docs/misc/xen-command-line.pandoc > @@ -2072,6 +2072,28 @@ for all of them (`true`), only for those subject to XPTI (`xpti`) or for > those not subject to XPTI (`no-xpti`). The feature is used only in case > INVPCID is supported and not disabled via `invpcid=false`. > > +### pdx-compress > +> `= | auto | fast | slow` > + > +> Default: `auto` > + > +Only relevant when hypervisor is build with PFN PDX offset compression > +`CONFIG_PDX_OFFSET_COMPRESSION`. > + > +Controls whether Xen will engage in PFN compression, and which algorithm will > +be used to calculate the compression coefficients: > + > +* `auto`: default choice, attempt fast calculation of compression > + coefficients, if that's not successful fallback to slow calculation. > + > +* `fast`: only attempt fast calculation of coefficients, if it fails PFN PDX > + compression will be disabled. > + > +* `slow`: only attempt slow calculation of coefficients, if it fails PFN PDX > + compression will be disabled. > + > +Note `pdx-compress=true` is equivalent to `pdx-compress=auto`. > + > ### ple_gap > > `= ` > > diff --git a/xen/common/pdx.c b/xen/common/pdx.c > index feabdcded804..5fd01305a7be 100644 > --- a/xen/common/pdx.c > +++ b/xen/common/pdx.c > @@ -19,6 +19,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -468,11 +469,40 @@ STATIC void __init pfn_offset_sanitize_ranges(void) > } > > #ifdef __XEN__ > +static enum { > + PDX_AUTO, /* Fast first, fallback to slow if fast is not successful. */ > + PDX_NO, /* Do not attempt compression. */ > + PDX_FAST, /* Only attempt fast calculation of compression parameters. */ > + PDX_SLOW, /* Only attempt slow calculation of compression parameters. */ > +} compress_mode __initdata; > + > +static int __init cf_check parse_pdx_param(const char *arg) > +{ > + int val; > + > + if ( !arg ) > + return -EINVAL; > + > + if ( (val = parse_bool(arg, NULL)) != -1 ) > + compress_mode = val ? PDX_AUTO : PDX_NO; > + else if ( !strcmp(arg, "auto") ) > + compress_mode = PDX_AUTO; > + else if ( !strcmp(arg, "fast") ) > + compress_mode = PDX_FAST; > + else if ( !strcmp(arg, "slow") ) > + compress_mode = PDX_SLOW; > + else > + return -EINVAL; > + > + return 0; > +} > +custom_param("pdx-compress", parse_pdx_param); > + > bool __init pfn_pdx_compression_setup(paddr_t base) > { > - bool use_slow = false; > + bool use_slow = compress_mode == PDX_SLOW; > > - if ( nr <= 1 ) > + if ( nr <= 1 || compress_mode == PDX_NO ) > return false; > > if ( nr > ARRAY_SIZE(ranges) ) > @@ -507,11 +537,11 @@ bool __init pfn_pdx_compression_setup(paddr_t base) > dprintk(XENLOG_DEBUG, > "Find PFN compression coefficients using %s algorithm failed\n", > use_slow ? "slow" : "fast"); > - if ( use_slow ) > + if ( compress_mode == PDX_FAST || use_slow ) > return false; > } > > - if ( use_slow ) > + if ( compress_mode == PDX_FAST || use_slow ) > break; > } > --------------B0Qy7QKMeOBJiRuzXBIFI7sN Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 8bit


On 6/11/25 7:16 PM, Roger Pau Monne wrote:
Allow controlling whether to attempt PDX compression, and which algorithm
to use to calculate the coefficients.  Document the option and also add a
CHANGELOG entry for the newly added feature.

Note the work has been originally done to cope with the new Intel
Sapphire/Granite Rapids, however the compression is not explicitly tied to
Intel or x86, and hence could be helpful on other architectures.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
 CHANGELOG.md                      |  3 +++
 docs/misc/xen-command-line.pandoc | 22 ++++++++++++++++++
 xen/common/pdx.c                  | 38 +++++++++++++++++++++++++++----
 3 files changed, 59 insertions(+), 4 deletions(-)
LGTM: Reviewed-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>

Thanks.

~ Oleksii


diff --git a/CHANGELOG.md b/CHANGELOG.md
index 23215a8cc1e6..48327f03078f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
      table or foreign memory.
 
 ### Added
+ - Introduce new PDX compression algorithm to cope with Intel Sapphire and
+   Granite Rapids having sparse memory maps.
+
  - On x86:
    - Option to attempt to fixup p2m page-faults on PVH dom0.
    - Resizable BARs is supported for PVH dom0.
diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc
index b0eadd2c5d58..06819576a06b 100644
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -2072,6 +2072,28 @@ for all of them (`true`), only for those subject to XPTI (`xpti`) or for
 those not subject to XPTI (`no-xpti`). The feature is used only in case
 INVPCID is supported and not disabled via `invpcid=false`.
 
+### pdx-compress
+> `= <boolean> | auto | fast | slow`
+
+> Default: `auto`
+
+Only relevant when hypervisor is build with PFN PDX offset compression
+`CONFIG_PDX_OFFSET_COMPRESSION`.
+
+Controls whether Xen will engage in PFN compression, and which algorithm will
+be used to calculate the compression coefficients:
+
+* `auto`: default choice, attempt fast calculation of compression
+  coefficients, if that's not successful fallback to slow calculation.
+
+* `fast`: only attempt fast calculation of coefficients, if it fails PFN PDX
+  compression will be disabled.
+
+* `slow`: only attempt slow calculation of coefficients, if it fails PFN PDX
+  compression will be disabled.
+
+Note `pdx-compress=true` is equivalent to `pdx-compress=auto`.
+
 ### ple_gap
 > `= <integer>`
 
diff --git a/xen/common/pdx.c b/xen/common/pdx.c
index feabdcded804..5fd01305a7be 100644
--- a/xen/common/pdx.c
+++ b/xen/common/pdx.c
@@ -19,6 +19,7 @@
 #include <xen/mm.h>
 #include <xen/bitops.h>
 #include <xen/nospec.h>
+#include <xen/param.h>
 #include <xen/pfn.h>
 #include <xen/sections.h>
 #include <xen/sort.h>
@@ -468,11 +469,40 @@ STATIC void __init pfn_offset_sanitize_ranges(void)
 }
 
 #ifdef __XEN__
+static enum {
+    PDX_AUTO, /* Fast first, fallback to slow if fast is not successful. */
+    PDX_NO,   /* Do not attempt compression. */
+    PDX_FAST, /* Only attempt fast calculation of compression parameters. */
+    PDX_SLOW, /* Only attempt slow calculation of compression parameters. */
+} compress_mode __initdata;
+
+static int __init cf_check parse_pdx_param(const char *arg)
+{
+    int val;
+
+    if ( !arg )
+        return -EINVAL;
+
+    if ( (val = parse_bool(arg, NULL)) != -1 )
+        compress_mode = val ? PDX_AUTO : PDX_NO;
+    else if ( !strcmp(arg, "auto") )
+        compress_mode = PDX_AUTO;
+    else if ( !strcmp(arg, "fast") )
+        compress_mode = PDX_FAST;
+    else if ( !strcmp(arg, "slow") )
+        compress_mode = PDX_SLOW;
+    else
+        return -EINVAL;
+
+    return 0;
+}
+custom_param("pdx-compress", parse_pdx_param);
+
 bool __init pfn_pdx_compression_setup(paddr_t base)
 {
-    bool use_slow = false;
+    bool use_slow = compress_mode == PDX_SLOW;
 
-    if ( nr <= 1 )
+    if ( nr <= 1 || compress_mode == PDX_NO )
         return false;
 
     if ( nr > ARRAY_SIZE(ranges) )
@@ -507,11 +537,11 @@ bool __init pfn_pdx_compression_setup(paddr_t base)
             dprintk(XENLOG_DEBUG,
                     "Find PFN compression coefficients using %s algorithm failed\n",
                     use_slow ? "slow" : "fast");
-            if ( use_slow )
+            if ( compress_mode == PDX_FAST || use_slow )
                 return false;
         }
 
-        if ( use_slow )
+        if ( compress_mode == PDX_FAST || use_slow )
             break;
     }
--------------B0Qy7QKMeOBJiRuzXBIFI7sN--