Azure Virtual VM: Hardware Reserved Memory Issue — Investigation and Troubleshooting

Deon Swart 0 Reputation points
2026-10-01T08:46:00.16+00:00

Problem description

I am experiencing an issue where my Azure Virtual VM resource shows memory as 'hardware reserved' and it cannot be released for normal Windows or AVD use. The memory reservation appears to be affecting only one session host, and Windows is not activated on this host. Despite rebooting and attempting configuration changes, the reserved memory issue persists. I am seeking guidance on resolving this memory reservation problem.

Environment

The issue involves Azure Virtual VM, specifically Windows-based virtual machine(s) used as session hosts. The affected host is not activated, and the problem appears isolated to a single session host. Specific environment details such as region, VM size, OS version, or whether multiple hosts are affected are not provided.

What I've already tried

I have rebooted the affected host, attempted changing server specifications, performed reset and redeploy procedures. No other troubleshooting steps, such as checking activation status, adjusting msconfig settings, or verifying network connectivity to KMS endpoints, have been documented or performed.

Current status

The issue remains unresolved. The most recent information suggests the problem may be related to Windows activation failure, preventing Windows from utilizing the full RAM, rather than a true Azure platform-level hardware reservation. Further diagnostic steps are needed to confirm activation status and memory configuration.

Windows for business | Windows Server | User experience | Other
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  1. Ronald Sabiiti 160 Reputation points Independent Advisor
    2026-10-01T09:35:28.3466667+00:00

    Hello @Deon Swart

    Welcome to Microsoft Q&A!

    Thank you for your patience, and taking the time to elaborate on your concerns.

    What you’re seeing memory marked as “hardware reserved” inside a Windows VM is almost never a true Azure hardware reservation. In most cases it’s a Windows activation or configuration issue that prevents the OS from using all available RAM.

    Why this happens

    • Activation failure: If Windows isn’t activated, certain features (including full RAM usage) can be restricted.
    • Boot configuration: msconfig or BCD settings can cap usable memory.
    • Driver/firmware mismatch: Rarely, VM drivers can misreport memory mapping, but in Azure this is uncommon.
    • Platform vs. guest: Azure allocates the full VM memory, but Windows inside the guest decides how much is usable. “Hardware reserved” is Windows’ way of saying it can’t map that memory for normal use.

    Steps to resolve

    1. Check activation status
      • Settings → Update & Security → Activation.
      • If it shows “Windows is not activated,” resolve licensing first. For Azure VMs, activation is automatic via KMS endpoints. Ensure outbound connectivity to kms.core.windows.net (TCP 1688).
    2. Force re‑activation
      • Run:
    powershell 

    slmgr /ato
    • If activation fails, check firewall/network rules to KMS.
    1. Verify boot configuration
      • Run:
      powershell

     msconfig
    • Under Boot → Advanced options, ensure “Maximum memory” is unchecked.
    1. Check Device Manager
      • Confirm no missing drivers for Hyper‑V synthetic devices. Outdated drivers can misreport memory mapping.
    2. Redeploy if needed
      • If activation and configuration checks don’t clear the issue, redeploy the VM from the same image. This resets activation and clears mis‑mapped memory.

    I hope this helps to better understand the diagnostic options available and the risks involved.

    If this information was helpful, please click Accept Answer.

    Thank you for choosing Microsoft Q&A.

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